Hector's dolphin description

Hector's dolphin, one of the rarest and smallest of marine dolphins (4), has a short, stocky torpedo-shaped body, which becomes narrow towards the tail. There is no discernible beak. The sides and back are light grey, there is a darker stripe along the middle, and the underside is white (5). The large tail flukes, flippers and characteristically rounded dorsal fin are all black. A black marking extends from the snout back around the eye reaching to the flipper. Males and females are similar in appearance, but females tend to be slightly longer than males (6). Calves have the same markings as adults, but foetal folds visible as pale lines on darker areas can also be seen on individuals less than six months old. The common name of this dolphin refers to the New Zealand scientist Sir James Hector, who first examined the species (7).

Related species

Hector's dolphin biology

This dolphin tends to occur in small groups of two to ten individuals. These groups sometimes join together forming larger temporary aggregations. Hector’s dolphins undertake short dives for about 90 seconds and feed on a variety of small fish and squid. Hector’s dolphins reproduce slowly and without human impacts have a maximum population growth rate of about 2 percent per year. Females reach maturity at around 7 to 9 years of age, and males between 5 and 9 years. Courtship behaviour involves close contact, leaping, chasing and belly displays. Each female has one calf every 2-4 years which tends to be born between late spring and summer (6). A maximum age of about 20-25 years has been observed. Hector’s dolphins are unusual in that they only produce short, high frequency clicks, not whistles like many other species of dolphin (7).

Hector's dolphin range

Endemic to New Zealand waters, this species is found around the majority of the South Island. The sub-species, Maui’s dolphin, is only found in a small area off the west coast of the North Island (8). The population size today is estimated to be 27 percent of its size in 1970, before a major expansion in commercial gillnetting (9). Following surveys carried out between 1997 and 2000, the total population around the South Island was estimated at about 7000 individuals (10)(11). The North Island subspecies’ population is much smaller than the South Island population, with approximately 100 individuals remaining (8).

Hector's dolphin threats

Currently the major threat to the survival of this species is bycatch by commercial and recreational fishers, particularly entanglements in gillnets, which is reported to occur throughout the range (1)(6)(9). Due to the coastal habitat of Hector's dolphin, the species is vulnerable to a large number of other threats such as pollution, vessel traffic and habitat modification as well as fisheries bycatch(1).

Hector's dolphin conservation

The New Zealand Marine Mammals Protection Act has made the deliberate killing or injury of marine mammals illegal (1). Under this act, the Department of Conservation designated the Banks Peninsula Marine Mammal Sanctuary in 1988, effectively prohibiting commercial gillnetting and restricting recreational gillnetting. A second protected area was designated on the west coast of the North Island in 2003. These were surpassed by new Ministry of Fisheries regulations in 2008 which ban gillnetting to four nautical miles off the majority of the South Island’s east and south coasts, regulate gillnetting on the South Island’s west coast to two nautical miles (3.7 kilometres) offshore and extend the gillnet ban on the North Island’s west coast to seven nautical miles (13 kilometres) offshore. Five marine mammal sanctuaries were designated around the coastline in 2008 to provide additional protection from non-fisheries related impacts (13).

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